When persons, such as skiers, hikers, mountaineers, hunters, snowmobilers, military personnel, etc., are moving around in nature there is risk, in particular during winter and spring, of accidents. In particular avalanches pose a life-threat to these persons. Portable rescue devices are often used by these persons, in order to increase the chances for them to be found when an accident has occurred that stops them from moving on. Often, and in particular in case of an avalanche, the victims cannot be seen or heard or are very difficult to see or hear. Then the portable rescue device may save lives by providing an electronic location system, which is useful independently of visible sight.
One prior art device is disclosed in U.S. Pat. No. 6,484,021 to Hereford et al. That prior art device is arranged for transmitting and receiving a signal from another rescue device. It uses two antennas mounted perpendicular to each other and a virtual third antenna for receiving a distress signal and for being able to determine, by means of a processor, an approximate direction and an approximate distance to the sending device. The direction is presented by means of five LEDs, one of which is illuminated to give a rough indication of the direction to the victim relative to the direction that the device is pointing at. The distance calculations are based on received signal strength. The rescue operation is often time critical. For every minute gained a life may be saved. The prior art solution provides rather wide margins of error both as regards the angle of direction towards the victim and as regards the distance to the victim.